A 25-year-old Caucasian man had experienced an upper respiratory infection in the past 10 days and now complains of dyspnea, cough, and hemoptysis. A routine complete blood count (CBC) shows hemoglobin 8 g/dL, mean cell volume 75 m3 (normal 80 to 96 m3); urinalysis showing microscopic hematuria with misshapen red cells and red cell casts. Serum creatinine is elevated at 2.8 mg/dL. Sputum examination shows hemosiderin-laden macrophages. Which of thefollowing laboratory studies is most likely to lead to the diagnosis of this condition?
(A) Antineutrophil cytoplasmic antibody (ANCA)
(B) Antiglomerular membrane antibodies
© BUN
(D) Antistreptolysin O antibodies (ASO)
(E) Fasting blood sugar (FBS)
The answer is B. Antiglomerular membrane antibodies (anti-AGB AB). The combination of glomerulonephritis and pulmonary hemorrhage along with anti-AGB AB antibodies defines Goodpasture disease. This a serious and potentially fatal disease whose treatment is best left to those who are experienced in critical care. In 90% of cases,anti-AGB AB antibodies are present. ANCAs are present in about 15%. Iron deficiency anemia is common, reflecting the significance of the blood loss through the lungs. While neither one is particularly specific, Goodpasture is the only acute autoimmune disease that involves both the kidneys and the lungs. Diabetes is not associated statistically. BUN and ASO are entirely nonspecific, albeit sensitive indicators of inflammation with autoimmune components